But, just as he worked himself over the edge of the boulder, what was his amazement to see a mountain goat, evidently descending from the cliff above, land with a clatter of hoofs on the rock not ten feet away from him. Rivers promptly scrambled to his feet, and the goat, apparently thinking himself cornered and facing boldly an unknown danger, rushed at him with lowered horns. A quick sideways jump was all that saved the geologist, and the goat nearly went headlong over the edge with his rush. For a minute or two Roger was in utter ignorance of what had happened, for being immediately under the rock while the chief was standing on his shoulders, he had not seen the goat leap down to dispute the supremacy of position with the unexpected intruder. Not till he heard Rivers call to him did he know that anything was wrong. "Doughty," he heard him say, "put a bullet in this infernal brute, will you?" The boy ran back to get a perspective view of the top of the boulder, and by climbing up the cliff a little way saw what had developed. In the meantime the position of the geologist was precarious in the extreme. A succession of short rushes he had narrowly escaped by dodging, but he knew that in a chase of this kind, he could not but lose, and if the goat should catch him with his horns not only would the injury be serious enough in itself, but probably he would be thrown from the rock to fall a distance of twenty feet to the icy and frost-bound ground below. Suddenly Rivers saw his opportunity, and as the goat paused to turn at the end of a futile rush, he seized his horns sideways with a firm grasp, in such wise that the creature could not get a purchase with which to butt, and determined to hang on for dear life. He purposed, if it could be managed, to drive the goat to the edge of the boulder, and then, by twisting its neck, force it over the edge. It was a doubtful chance, but the only one he could see. In the meantime Roger was cudgeling his brain for some means of climbing the rock, but to no purpose, and he could have bitten his nails in sheer vexation of spirit at his inability to give any aid, with his friend in so great peril a few steps away. The boy watched and waited in the chance of getting a shot at the goat, but found it difficult to find an opportunity. Once, indeed, he fired, feeling sure that he could hit the animal's flank, but he was not certain enough of his prowess with a revolver to risk a shot when he was just as likely to hit his chief as he was the goat. Once, indeed, the boy thought Rivers had his foe, for he forced him to the edge of the boulder and put all his strength into a violent wrench. But a mountain goat, though not large, is possessed of considerable strength, and in his effort to free himself almost sent Rivers over the edge.